using System;

using System.Collections;

using System.Collections.Generic;

​

class Space

{

    public int i;

}

​

class Column : IEnumerable<Space>

{

    public Space[] Spaces;

    public IEnumerator<Space> GetEnumerator()

    {

        //this works too

        //return((IEnumerable<Space>)this.Spaces).GetEnumerator();

        foreach(Space s in this.Spaces)

            yield return s;

    }

    IEnumerator<Space> IEnumerable<Space>.GetEnumerator()

    {

        return (IEnumerator<Space>)GetEnumerator();

    }

    IEnumerator IEnumerable.GetEnumerator()

    {

        throw new NotImplementedException();

    }

}

​

public class Program

{

    public static void Main()

    {

        Column c = new Column();

        c.Spaces = new Space[]{new Space(){i=1}, new Space(){i=2}};

        foreach(Space s in c)

            Console.WriteLine(s.i);

    }

}